An image pickup lens has been developed so far which is made up of six lenses including a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens that are arranged in this order from an object side toward an image plane side. Further, attention has been given to arranging, in the image pickup lens, the sixth lens so that a surface of the sixth lens which surface is located on the image plane side (hereinafter, also referred to as an “image plane-side surface”) is as close as possible to an image plane, mainly for the purpose of (i) causing the sixth lens to effectively correct various aberrations and (ii) making an optical overall length shorter.
An image pickup lens disclosed in Patent Literature 1 employs a sixth lens whose image plane-side surface is an optically planar surface. This makes it possible to arrange the sixth lens so that the entire image plane-side surface is close to an image plane. Note that examples of the “optically planar surface” include a structurally planar surface, a surface which is obtained by forming, on such a structurally planar surface, minute unevenness (for example, of the order of nanometers) that causes a reduction in reflectance of light, and a surface which is obtained by slightly curving such a structurally planar surface. These surfaces have a common feature that a change in light transmission or a resultant change in optical characteristic (such as refractive power or eccentricity) is so small as to be neglected in an image pickup lens.